Spinal balance assessment

ABSTRACT

The present application describes computer apparatus and software programs useful to the field of corrective spinal surgery. The apparatus and software implement and facilitate methods for assessing the degree of balance and alignment achieved through corrective measures applied to the spine prior to completing a surgical procedure. The apparatus and software facilitate pre-operative planning and virtual testing of the corrective measures to be applied. The apparatus and software further facilitate intra-operative reconciliation with the pre-operative plan prior to completing the surgery.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. Pat. No. 9,968,408filed Mar. 17, 2014 and issued on May 15, 2018, which claims priority toU.S. Provisional Application Ser. No. 61/802,180 filed on Mar. 15, 2013,the entire contents of which is hereby incorporated by reference intothis disclosure as if set forth fully herein.

FIELD

The present invention relates to the field of corrective spinal surgery,including a system and associated methods for assessing the degree ofbalance and alignment achieved through corrective measures applied tothe spine prior to completing the surgical procedure.

BACKGROUND

The spine is formed of a column of vertebra that extends between thecranium and pelvis. The three major sections of the spine are known asthe cervical, thoracic and lumbar regions. There are 7 cervicalvertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae, with each ofthe 24 vertebrae being separated from each other by an intervertebraldisc. A series of about 9 fused vertebrae extend from the lumbar regionof the spine and make up the sacral and coccygeal regions of thevertebral column.

The main functions of the spine are to provide skeletal support andprotect the spinal cord. Even slight disruptions to either theintervertebral discs or vertebrae can result in serious discomfort dueto compression of nerve fibers either within the spinal cord orextending from the spinal cord. Disruptions can be caused by any numberfactors including normal degeneration that comes with age, trauma, orvarious medical conditions. If a disruption to the spine becomes severeenough, damage to a nerve or part of the spinal cord may occur and canresult in partial to total loss of bodily functions (e.g., walking,talking, breathing, etc.). Therefore, it is of great interest andconcern to be able to treat and correct ailments of the spine.

When conservative efforts fail, treating spinal ailments very oftenincludes a combination of spinal fusion and fixation. Generally, spinalfusion procedures involve removing some or all of an intervertebraldisc, and inserting one or more intervertebral implants into theresulting disc space. Introducing the intervertebral implant serves torestore the height between adjacent vertebrae (“disc height”) andmaintain the height, and/or correct vertebral alignment issues, untilbone growth across the disc space connects the adjacent vertebralbodies. During such procedures resection of ligaments and/or boneyelements from the affected spinal area is common in order to access thedisc space and/or decompress impinged nerve or spinal cord tissue.Though generally necessary to achieve the aims of the surgery, theresection of ligaments and/or boney tissue along the spine introducesinstability (or, oftentimes, increased instability) to the spine.

Fixation systems are often surgically implanted during a fusionprocedure to help stabilize the vertebrae to be fused until the fusionis complete or to address instabilities (either preexisting or createdby the fusion or decompression procedure itself). Fixation constructs ofvarious forms are well known in the art. Fixation systems usually use acombination of rods, plates, pedicle screws, and bone hooks to create afixation construct across affected vertebrae. These fixations systemsare designed to engage either the posterior elements (e.g. pedicle screwsystems, spinous process plates) or anteriorly, the vertebral bodies(e.g. plates, anterior staple/rod systems). The configuration requiredfor each procedure and patient varies due to the ailment being treated,the specific method of treatment (e.g. surgical approach, etc. . . . )and the patient's specific anatomical characteristics. Like the fusion,the fixation system can be implanted across a single level or acrossmultiple levels, and typically, the fixation system is positioned tospan at least each level to be fused. In severe cases the fixationconstruct may stretch along the majority of the spine.

Despite the tremendous benefits gained by patients (e.g. a reduction orelimination of symptoms such as pain, poor posture, etc. . . . ) whichcan be credited to the fusion/fixation procedures, the procedures arenot without disadvantages. For example, the loss of motion at one ormore levels of the spine increases the loads placed on remaininguntreated levels. These increased loads can hasten a breakdown at nearbyuntreated levels (commonly referred to as adjacent level disease), or,cause a hardware failure in which a portion of the spinal fixationconstruct breaks, generally leading to a failed fusion and instability.The importance of spinal balance as a determinant factor for positivesurgical outcomes (those that avoid or limit the effects just describedand result in a positive reduction of symptoms) is increasingly beingrecognized. Spinopelvic measurements have been identified as criticalparameters to consider when evaluating overall balance. Several studiescorrelate worsening HRQL (Health Related Quality of Living) parameterswith positive postoperative sagittal balance (defined as SVA>5 cm,PT>20°, PI≠LL±9°), where SVA=sagittal vertical axis, PT=pelvic tilt, andPI=pelvic incidence. Other relevant anatomical measurements includeK=thoracic kyphosis, LL=lumbar lordosis, SA=sagittal alignment,CA=coronal alignment, T1-tilt. Tools to help the surgeon assessintraoperative changes in overall balance however are lacking. The toolsand methods set forth herein are directed towards addressing thesechallenges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart depicting the network cloud structure utilizedwith the spinal balance assessment application described herein,according to one example embodiment;

FIG. 2 is a flow chart depicting a preoperative module of the spinalbalance assessment application described herein, according to oneexample embodiment;

FIG. 3 is a flow chart depicting a surgical planning module of thespinal balance assessment application described herein, according to oneexample embodiment;

FIG. 4 is a flow chart depicting an intraoperative module of the spinalbalance assessment application described herein, according to oneexample embodiment;

FIG. 5 is a flow chart depicting a postoperative module of the spinalbalance assessment application described herein, according to oneexample embodiment; and

FIG. 6 is one example of a method for utilizing the spinal balanceassessment application described herein for to ensure overall balanceduring a corrective spinal procedure.

DETAILED DESCRIPTION

The present application describes a balance assessment application thatmay be utilized by the surgeon before, during, and after surgery toensure overall balance is achieved and maintained by the surgicalprocedure. The balance application includes a secure software packageuseable on portable computing devices (and preferably workstations aswell) that manages patient data (images, relevant clinical information)and provides a platform for perioperative assessment and treatment. Theapplication includes modules for preoperative, intraoperative, andpostoperative surgical measurement of anatomy, as well as manipulationand reconstruction of collected images.

With reference to FIG. 1, the balance assessment application utilizes anetwork structure (e.g. internet based cloud computing) that links anumber of computer devices and diagnostic tools together over theinternet. This structure enables secure data storage and transfer ofdiagnostic images for viewing on various computing devices (e.g.personal computers, tablets, or smart phones) and allows surgeons toaccess a patient's medical images at any time, with a variety of devicesand on a variety of platforms to perform the clinical measurements forpreoperative planning, intraoperative assessment and postoperativefollow up. The surgeon can perform anatomical measurements directly onthe mobile device, or on a separate workstation and then access themeasurements later on the mobile device. The surgeon can also simulatethe effects of surgical manipulations on postoperative alignment (e.g.simulate the effect of a 25° pedicle subtraction osteotomy) to maximizethe surgeons ability to achieve overall balance. The balance assessmentapplication may also utilize spatial mapping technology to evaluateintraoperative changes in alignment by tracking the location ofanatomical landmarks. The spatial mapping technology may be similar tothat described in U.S. patent application Ser. No. 13/815,643, filedMar. 12, 2013 (“643 application”), which is incorporated herein byreference. It will be appreciated that the systems and softwaredescribed in the Mar. 12, 2013 application may be used in conjunctionwith the spinal balance application described herein or may beintegrated with the spinal balance application. It will also beappreciated that any of features, functions, tools, interfaces, etc. . .. described in the in the '643 application may be utilized in the spinalbalance application to accomplish the same or related goals (e.g. spinalmeasurements, virtual manipulations, virtual reconstructions, etc. . . .).

The spinal balance application includes a preoperative module, aplanning module, an intraoperative module, and postoperative module.With reference to FIG. 2, the preoperative module will now be described.The preoperative module begins with image acquisition. Pre-operativeimages (e.g. plain film radiographs, CAT, MRI, PACS) are acquired fromthe hospital, doctors office, archive, etc . . . , and ported to themobile device (e.g. laptop, tablet, smartphone) or other workstation.Optionally, the software package includes image recognition algorithmsto detect bone in the images and automatically segments the bony anatomysuch that the visual output only includes the bone structures. Metricsare performed on the bone structures to determine one or more of theanatomical measurements noted above. The metrics may be performedmanually by the surgeon or assistant on a mobile device or workstation.By way of one example the software may include a GUI and themeasurements may be calculated using the GUI. Still by way of example,the GUI may include the Virtual Protractor mode (or similar variation ormodification) described in the '643 application. Alternatively, themetrics may be calculated automatically by algorithms in the software.

The surgical planning module is described now with reference to FIG. 3.Using the workstation (or mobile device if the processing power permits)a virtual reconstruction of the segmented anatomy may be performed.Using the GUI, the surgeon may resect boney anatomy, add implants (e.g.interbody devices, pedicle screws, rods, plates, etc. . . . ), andmanipulate the position or alignment of anatomy. Metrics are performedto show the effects of the virtual surgery. Different degrees ofmanipulation, implant dimensions, and combinations thereof may betrialed until the desired correction and balance is achieved. Thesurgical plan (i.e. implant sizes, levels, resections, alignmentmanipulations, etc. . . . ) used to achieve the correction are saved forreferral during the live surgery.

The intraoperative module is described with reference to FIG. 4. Theintraoperative module begins with image porting of the surgical plan andpreoperative imaging to the mobile device. Image acquisition (typicallyC-arm radiographs) occurs throughout the procedure as required and theimages are ported to the mobile device or in O.R. workstation ifavailable (it is noted that the processing system described in the '643application may be utilized as the in O.R. workstation). The images areautomatically segmented to provide easier visualization. The surgicalplan can be viewed on the mobile device and followed during the livesurgery to attempt to achieve the same correction and balance. Metricsare performed (again either manually as noted above, or automatically bythe software) to reconcile the actual output with the virtual output. Ifthe actual output does not comport with the virtual output, the surgeonmay continue the operation and adjust one or more parameters of thereconstruction. This process may be repeated until the appropriatecorrection and balance is obtained.

The postoperative module is shown with reference to FIG. 5. Thepostoperative module is substantially similar to the preoperativemodule. However, in the postoperative module the postoperative metricscan be compared to the intraoperative metrics. This not only provides anongoing assessment as to the overall balance of the spine, but it alsoprovides data which can be collected and analyzed to aid in subsequentplanning sessions. By way of example, FIG. 6 depicts one example methodfor using the spinal balance assessment application to ensure overallbalance during a corrective spinal procedure.

While specific embodiments have been shown by way of example in thedrawings and described herein in detail, it will be appreciated that theinvention is susceptible to various modifications and alternative forms(beyond combining features disclosed herein). The description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the invention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

What is claimed is:
 1. A method for assessing spinal balance during asurgical procedure executed on a surgical site on the spine of apatient, the method comprising: uploading into a processor based workingplatform, a first image of the surgical site related anatomy;identifying at least one spinal metric for assessing spinal balanceselected from the group comprising: sagittal vertical axis, pelvic tilt,pelvic incidence, thoracic kyphosis, lumbar lordosis, sagittalalignment, coronal alignment, or tilt; determining a first numeric valueof the at least one spinal metric from the preoperative image, saiddetermining step comprising acquiring a first digital position of two ormore spinal landmarks defining the spinal metric, generating one or morefirst lines between the spinal landmarks, and determining a firstnumeric relationship between the spinal landmarks; determining a desiredreconstruction numeric value of the at least one spinal metric based onthe determined first numeric value, said determining step comprisingidentifying one or more parameters for achieving a desired correctionand a desired balance; performing a surgical correction on the surgicalsite based on the identified one or more parameters; capturing a secondimage of the surgical site; determining a second numeric value of the atleast one spinal metric from the second image, said determining stepcomprising acquiring an second digital position of two or more spinallandmarks defining the spinal metric, generating one or more secondlines between the spinal landmarks, and determining a second numericrelationship between the spinal landmarks; and reconciling the secondnumeric value of the at least one spinal metric from the second imagewith the desired reconstruction numeric value of the at least one spinalmetric.
 2. The method of claim 1, wherein the working platformautomatically segments the first image to display only boney anatomy. 3.The method of claim 1, wherein the working platform automaticallysegments the second image to display only boney anatomy.
 4. The methodof claim 1, wherein the step of determining at least one spinal metricon the working platform is performed manually.
 5. The method of claim 1,wherein the step of determining at least one spinal metric on theworking platform is performed automatically by the working platform. 6.The method of claim 1, wherein the step of reconciling the secondnumeric value of the at least one spinal metric from the second imagewith the desired reconstruction numeric value of the at least one spinalmetric includes determining that the desired correction was not achievedand repeating the steps of performing a surgical correction on thesurgical site based on the identified one or more parameters,determining a corrected numeric value of the at least one spinal metricfrom the second image, reconciling the corrected numeric value of the atleast one spinal metric from second image with the desiredreconstruction numeric value of the at least one spinal metric.
 7. Themethod of claim 1, including the additional steps of capturing a thirdimage of the surgical site, determining a third numeric value of the atleast one spinal metric from the third image, and comparing the thirdnumeric value of the at least one spinal metric from the third imagewith the second numeric value of the at least one spinal metric from thesecond image.